Preparation of Lateral Organic Spin-valve Devices with La0.7Sr0.3MnO3
- PDF / 149,030 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 49 Downloads / 194 Views
1033-J04-04
Preparation of Lateral Organic Spin-valve Devices with La0.7Sr0.3MnO3 Tomonori Ikegami1, Iwao Kawayama2, Masayoshi Tonouchi2, Yoshiro Yamashita3, and Hirokazu Tada1 1 Osaka University, Toyonaka, Japan 2 Osaka University, Suita, Japan 3 Tokyo Institutes of Technology, Yokohama, Japan ABSTRACT Spin injection and transport characteristics of low-molecular-weight organic semiconductors such as pentacene and bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT) have been studied utilizing lateral type spin-valve devices with half metal electrodes, La0.67Sr0.33MnO3 (LSMO). The LSMO electrodes with a spacing of 200 nm were prepared by electron-beam lithography and dry etching of the epitaxial films grown on MgO substrates. The devices showed clear spin-valve behaviors with a magneto-resistance (MR) ratio up to 29 % at 9.1K. It was found that the MR ratio depended on the crystallinity of organic films as well as on temperature and applied bias voltages.
INTRODUCTION Considerable attention has recently been paid to the study of the active control and manipulation of spin degrees of freedom in organic materials (OMs) [1-12]. Spin relaxation times in OMs are expected to be relatively long owing to the weak spin-orbit coupling, which makes it possible to preserve spin coherence for a much longer period than in inorganic materials. This has been demonstrated in several reports on a magnetic field effect of electrical properties in layered and lateral-type sandwich structures composed of ferromagnetic (FM) electrodes and OMs including 8-hydroxy-quinoline aluminum (Alq3) [2,3], poly-3hexylthiophene [4], tetrapheyl-porphyrin [5], and sexithienyl [6]. Long spin coherence was demonstrated in spin-valve devices based on carbon nanotubes [7-9], and graphene sheets [10]. Lateral structures are more attractive since various functions such as an electric field effect can be integrated in the devices. In the present study, we have prepared the lateral-type sandwich structures composed of La0.67Sr0.33MnO3(LSMO) and low-molecular-weight OMs such as pentacene (Fig. 1(a)) and bis(l,2,5-thiadiazolo)-p-quinobis(l,3-dithiole) (BTQBT, Fig. 1(b)), and studied the magnetic filed effect on electric properties.
EXPERIMENT LSMO films were grown epitaxially on MgO by pulsed laser deposition [13]. Figure 1(c) shows a schematic illustration of the prepared substrate. LSMO films with a thickness of approximately 100 nm were patterned on a pair of rectangular electrodes with dimensions of 1 mm × 0.5 mm by electron-beam lithography and dry etching. The spacing between the
electrodes was 200 nm. When the etching of LSMO did not proceed perfectly, thin LSMO layers that remained exhibited some conductivity. Such devices showed an anisotropic magnetoresistance (MR) under magnetic fields, but did not show spin-valve characteristics as shown in Fig. 1(d). Pentacene and BTQBT are a class of materials that have high carrier mobilities owing to their high crystallinity in films prepared under appropriate growth conditions. They were evaporated on t
Data Loading...
